Flight of the Conchords' Bret McKenzie - fresh from writing songs for The Muppet Movie – has landed one of his biggest film roles, in a comedy to be shot in Southland next month.

The Wellington actor and musician will star in Two Little Boys alongside Australian comedian Hamish Blake, best known for the TV series Hamish and Andy.

The film, set in Invercargill and the Catlins, will be directed by Robert Sarkies, who has co-written the script with brother Duncan Sarkies, based on the Duncan Sarkies novel of the same name.

It is the first time the Wellington-based brothers have worked on a film together since their breakout hit Scarfies in 1999.

McKenzie told The Dominion Post he had been offered parts in American movies, but had turned them down because he did not think their scripts up to scratch. But the Sarkies' screenplay impressed. "I've read a lot of scripts and this is by miles the best script I've read so it's really exciting."

In Two Little Boys, McKenzie plays Nige and Blake is Deano, his recently estranged best mate. Their long-term friendship is put under pressure by "an unfortunate accident" involving a hot meat pie, a ginger cat and the untimely death of a Scandinavian football star.

McKenzie said that though it was a comedy, it had a more dramatic edge than his previous roles.

"The film is far more extreme. It does things we would never do in Conchords. "Nige accidentally runs over a Scandinavian backpacker and it's about him and his friend Deano trying to get rid of the body." The film was set in the early 1990s. "It's pre-internet, pre-cellphones. New Zealand was isolated at that time in a way that it isn't any more ... I imagine Invercargill [then] was another step towards nowhere."

Invercargill Mayor Tim Shadbolt will play the city's mayor.

McKenzie has spent the past few months in Los Angeles as music supervisor for The Muppet Movie, due for release next year. He has contributed several songs.

"It was really unexpected. We were in the studio recording Kermit the Frog and Miss Piggy. It was a very surreal experience."

McKenzie said he and Jemaine Clement also wanted live Flight of the Conchords shows in New Zealand next year, but it would depend on schedules. Clement has been working on Men in Black III.

Boy star and director Taika Waititi, who starred in Scarfies and directed episodes of Flight of the Conchords, is to direct the pilot for an American remake of British sitcom The Inbetweeners. The British series was co-written by Iain Morris, who also wrote some Flight of the Conchords episodes.